Flash layer overcoat for magnetically-induced super resolution magneto-optical media

ABSTRACT

Magnetically-induced, super-resolution (MSR), magneto-optical (MO)information storage media having improved tribological properties when used in high-density storage devices employing very small head flying heights are formed by providing a protective flash layer overcoat (FLO)/lubricant topcoat layer system on the media surface. Embodiments of the present invention include forming the FLO layer of an amorphous, abrasion-resistant, carbon-based, diamond-like material not greater than about 10 Å thick and selected from CN x , CH x , and CN x H y , and providing the lubricant topcoat as an about 15-25 Å thick layer of a fluoropolyether or perfluoropolyether compound e.g., perfluoropolyethylene (PFPE).

CROSS-REFERENCE TO PROVISIONAL APPLICATION

[0001] This application claims priority from provisional patentapplication Serial No. 60/107,698 filed Nov. 9, 1998, the entiredisclosure of which is incorporated herein by reference.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application contains subject matter similar to subjectmatter disclosed in co-pending U.S. patent application Ser. No. ______,filed on ______ (Attorney Docket No. 50103-252), Ser. No. ______, filedon ______ (Attorney Docket No. 50103-253); and Ser. No. ______, filed on(Attorney Docket No 50103-253).

FIELD OF THE INVENTION

[0003] The present invention relates to the recording, storage, andreading of information utilizing magneto-optical (MO) media,particularly rotatable MO storage media, such as in the form of thinfilm disks, and a protective overcoat/lubricant topcoat layer system forcontact with cooperating transducer and/or sensor heads or devices.

BACKGROUND OF THE INVENTION

[0004] In recent years, much research and development of MO recordingmedia for use as high density/high capacity memory devices has beencarried out. Such media typically comprise a suitable substrate, e.g.,of glass, polymer, metal, or ceramic material, coated with aperpendicularly magnetizable film used as a recording medium.Information is recorded within the medium by switching the direction ofmagnetization of desired portions (i.e., domains) of the perpendicularlymagnetizable film. More specifically, for recording information, therecording medium is first initialized by applying to the medium amagnetic field from an externally positioned magnetic field generationdevice (i.e., external magnetic bias), thereby making the direction ofthe perpendicular magnetization uniformly upwardly or downwardly facing.A first laser beam of sufficiently high power or intensity from asuitable source, e.g., a laser diode, is then irradiated on desiredrecording portions of the recording medium in the presence of anexternally applied magnetic bias field. As a consequence of the laserbeam irradiation, the temperature of the irradiated portions (domains)of the recording medium rises, and when the temperature reaches orexceeds the Curie point of the vertically magnetizable film or itsmagnetic compensation point, the coercive force on the recording portionbecomes zero or substantially zero. When this state is achieved at thedesired recording portions of the medium, and in the presence of theexternally biased magnetic field, the direction of the perpendicularmagnetization is switched, e.g., from upwardly facing (=digital logic 1or 0) to downwardly facing (=digital logic 0 or 1, respectively) or viceversa, so as to be aligned with that of the external magnetic field. Atthe end of a write pulse (i.e., laser pulse), the temperature of theheated recording domain then decreases and eventually returns to roomtemperature by cessation of the laser beam irradiation thereof. Sincethe alignment direction of magnetization of the recording media effectedby the laser pulse heating to above the Curie temperature is maintainedat the lowered temperature, desired information can thus be recorded inthe magneto-optical media.

[0005] For reading the information stored in the MO media according tothe above-described method, the recorded portions of the media areirradiated with a second, linearly polarized laser beam of lower poweror intensity than the one used for recording, and light reflected ortransmitted from the recorded portions is detected, as by a suitabledetector/sensor means. The recorded information is read out by detectingthe Kerr rotation angle of the polarization plane of light reflectedfrom the recording layer or the Faraday rotation angle of thepolarization plane of light transmitted through the recording layer.More particularly, since the rotation angle of the polarization planevaries depending upon the direction of magnetization of the recordedportions of the media according to the Kerr or Faraday effect,information stored within the media can be read out optically by adifferential detector which decodes the polarization-modulated lightbeam into bits of information

[0006] Such MO recording media, when fabricated in disk form forrotation about a central axis, can be adapted for use in conventionalWinchester, or hard drive, devices as are employed with conventionalmagnetic recording media. Hard drives typically employed for suchdisk-shaped media utilize flying heads for mounting transducer/sensordevices, etc., thereon, for close positioning thereof adjacent thesurface of the recording media. In operation, a typical contactstart/stop (CSS) method commences when a data transducing head begins toslide against the surface of the disk as the disk begins to rotate. Uponreaching a predetermined high rotational speed, the head floats in airat a predetermined small distance from the surface of the disk, where itis maintained during reading and recording operations. Upon terminatingoperation of the disk drive, the head again begins to slide against thesurface of the disk and eventually stops in contact with and pressingagainst the disk. Therefore, as in the case of magnetic disks, alubricant (optionally with an underlying protective layer) is typicallyapplied to the disk surface for minimizing scratching and abrasion ofthe sensor/transducer head and the recording media surface, which canresult in an undesirably high wear rate of the head and recording mediasurface.

[0007] However, in the case of portable MO recording devices, the use ofa lubricating oil, e.g., a fluorocarbon-based oil, is problematic inthat it is difficult to maintain the lubricating oil on the surface ofthe MO media, thereby increasing surface scratching and wear. Inaddition, MO disks produced without lubricating oil on their surface bysome manufacturers are not necessarily compatible with similar mediaproduced with lubricating oil by other manufacturers.

[0008] In another approach for minimizing abrasion, scratching, and wearof transducer heads, a solid lubricant is applied to the bottom surfaceof the flying head which comes into contact with the surface of the MOrecording medium. However, such solid lubricant applied to the bottomsurface of the flying head must have a durability many times greaterthan lubricant applied to the MO recording medium. As a consequence,application of solid lubricant only to the flying head is not sufficientfor adequately reducing abrasion, scratching, and wear

[0009] An additional difficulty encountered in the development ofwear-resistant, lubricated MO recording media and Winchester-type drivestherefor, is the requirement imposed by the impetus for achievingever-higher density recording, which necessitates further reduction inthe disk-transducer/sensor spacing. The head-to-disk interface (HDI)becomes very critical as head-disk spacing is reduced and head flyheight decreases. Conventional MO media without a protective overcoatand lubricant layer have extremely poor tribological performance,resulting in lack of reliability of MO-based disk drives.

[0010] The above-described problems, including disk crashing during headloading, associated with the requirement for reduced head-disk spacingand fly height, are further exacerbated in the case ofmagnetically-induced super resolution (“MSR”) MO media wherein enhancedrecording density is provided by interposing an exchange coupling forcelayer or a static coupling layer between the MO writing and read-outlayers, as will be further described in more detail below.

[0011] Thus, there exists a need for a protective overcoat or protectiveovercoat/lubricant topcoat layer system which enables the manufacture ofreliable, very high density recording magnetically-induced,super-resolution, MO-based disk drives, which layer system effectivelyeliminates the problems and drawbacks associated with the conventionaltechnology, i.e., scratching, abrasion, brittleness, increased wear oftransducer/sensor head and recording media surfaces, and tendency forcrashing during head loading.

[0012] The present invention addresses and solves the problems attendantupon the use of magnetically induced, super-resolution, MO-baseddisk-shaped recording media and hard drives, while maintaining fullcompatibility with all mechanical aspects of conventional disk drivetechnology.

DISCLOSURE OF THE INVENTION

[0013] An advantage of the present invention is a high density,magnetically-induced, super-resolution, MO-based recording medium havingimproved tribological performance and long-term durability.

[0014] Another advantage of the present invention is amagnetically-induced, super-resolution, MO-based recording medium havingan improved protective overcoat layer

[0015] A further advantage of the present invention is amagnetically-induced, super-resolution, MO-based recording medium havingan improved protective overcoat/lubricant topcoat layer system.

[0016] Yet another advantage of the present invention is amagnetically-induced, super-resolution, MO-based, disk-shaped recordingmedium providing improved performance at decreased head-to-diskspacings.

[0017] Still another advantage of the present invention is single- anddual-sided magnetically-induced, super-resolution, MO-based media havingprotective overcoat layer/lubricant topcoat layer systems thereonproviding improved tribological performance.

[0018] Additional advantages and other features of the present inventionwill be set forth in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of thepresent invention. The advantages of the present invention may berealized and obtained as particularly pointed out in the appendedclaims.

[0019] According to one aspect of the present invention, the foregoingand other advantages are obtained in part by a magnetically-induced,super-resolution, MO storage medium including at least one laminate oflayers comprising, in sequence from a substrate surface: an MO writinglayer; an MO exchange coupling layer or a dielectric layer formagneto-static coupling between the MO writing layer and a MO read-outlayer for increasing the recording density; an MO read-out layer; adielectric layer which is transparent to the wavelength(s) of at leastone laser beam used for writing and reading out information stored inthe medium; and an amorphous, abrasion resistant, carbon-basedprotective overcoat layer over the transparent dielectric layer.

[0020] According to embodiments of the present invention, the amorphous,abrasion resistant protective overcoat layer has a thickness not greaterthan about 10 Å thick, e.g., from about 5 to about 10 Å and comprises adiamond-like material selected from a-CN_(x), a-CH_(x), anda-CN_(x)H_(y); and the laminate further comprises a lubricant topcoatlayer on the protective overcoat layer, the lubricant topcoat layercomprising a fluoropolyether or a perfluoropolyether compound and havinga thickness of from about 15 to about 25 Å.

[0021] According to further embodiments of the present invention, thesubstrate includes a pair of opposed major surfaces and comprises amaterial selected from the group consisting of: polymers, metals, glass,and ceramics; the laminate of layers comprises a set of layers formed onone of the pair of opposed major surfaces, the layer set comprising, inoverlying sequence from the substrate:

[0022] (a) a reflective, heat sinking layer formed on one of the pair ofopposed major surfaces of the substrate;

[0023] (b) a first dielectric layer comprising a material which issubstantially transparent to the at least one laser beam wavelength;

[0024] (c) an MO auxiliary, writing assist layer comprising a rareearth/transition metal (RE/TM) material;

[0025] (d) an MO writing layer comprising an RE/TM thermo-magneticmaterial having perpendicular anisotropy, large perpendicularcoercivity, and high Curie temperature;

[0026] (e) an MO exchange coupling layer comprising an RE-TM material,for replicating the magnetic orientation of the MO writing layer andthereby increasing the coupling force between the MO writing layer andthe MO read-out layer; or

[0027] (f) a second dielectric layer comprising a material which issubstantially transparent to the at least one laser beam wavelength andperforms magneto-static coupling between MO writing and read-out layers;

[0028] (g) an MO read-out layer comprising an RE-TM material having asmall coercivity; and

[0029] (h) a third dielectric layer comprising a material which issubstantially transparent to the at least one laser beam wavelength;

[0030] wherein the protective overcoat layer is formed on the thirddielectric layer and the lubricant topcoat layer is formed over theprotective overcoat layer.

[0031] According to embodiments of the present invention:

[0032] the reflective, heat sinking layer (a) comprises aluminum (Al) oran alloy thereof;

[0033] each of the first, second, and third substantially transparentdielectric layers (b), (f), and (h) comprises a material selected fromthe group consisting of: SiN_(x), AlN_(x), SiO_(x), and AlO_(x);

[0034] the MO auxiliary, writing assist layer (c) comprises an RE-TMmaterial selected from the group consisting of: TbFe, TbFeCo, and FeCoX,where X is Dy, Gd, or Sm;

[0035] the MO writing layer (d) comprises an RE-TM material selectedfrom the group consisting of: TbFe, TbFeCo, TbFeCoX, TbDyFeCo, andTbDyFeCoX, where X is Al, Y, or Nd, and DyFeCoX, where X is Y, Nd, orAl;

[0036] the MO exchange coupling layer (e) comprises an RE-TM materialselected from the group consisting of: Gd, GdFe, GdFeSi, and GdFeAl; and

[0037] the MO read-out layer (g) comprises an RE-TM material havingin-plane magnetization at room temperature, selected from the groupconsisting of: GdFeCo and GdFeCoX, where X is Al, Nd, or Y, andGdFeCoXX′, where X is Al, Nd, or Y and X′ is Cr, Ta, or Nb.

[0038] In a further embodiment according to the present invention, themedium comprises another layer stack, identical to the above-describedlayer stack, formed on the other one of the pair of opposed majorsurfaces of the substrate.

[0039] According to another aspect of the present invention, amagnetically-induced, super-resolution magneto-optical (MO) storagemedium includes at least one laminate of layers comprising, in sequencefrom a substrate surface, an MO writing assist layer, an MO writinglayer, an MO exchange coupling layer or a magneto-static coupling layerfor increasing the writing density, an MO read-out layer, and adielectric layer which is substantially transparent to the wavelength(s)of at least one laser beam used for writing and reading-out informationstored in the medium, the medium further comprising:

[0040] an amorphous, abrasion-resistant, carbon-based, protectiveovercoat over the transparent dielectric layer, the protective overcoatlayer having a thickness not greater than about 10 Å and comprising adiamond-like material selected from the group consisting of a-CN,a-CH_(x), and a-CN_(x)H_(y); and

[0041] a lubricant topcoat layer having a thickness of from about 15 toabout 25 Å on the protective overcoat layer, the lubricant topcoat layercomprising a fluoropolyether polymer or a perfluoropolyether polymer.

[0042] According to yet another aspect of the present invention, amagnetically-induced, super-resolution (MSR), magneto-optical (MO)storage medium includes:

[0043] a substrate; and

[0044] means for protecting the exterior surface of the medium.

[0045] Additional advantages of the present invention will becomereadily apparent to those skilled in the art from the following detaileddescription, wherein only preferred embodiments of the invention areshown and described, simply by way of illustration of the best modecontemplated for practicing the present invention. As will be described,the present invention is capable of other and different embodiments, andits several details are susceptible of modification in various obviousrespects, all without departing from the spirit of the presentinvention. Accordingly, the drawing and description are to be regardedas illustrative in nature, and not as limitative.

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The following detailed description of the embodiments of thepresent invention can best be understood when read in conjunction withthe following drawings, in which like reference numerals are employedthroughout to designate similar features, wherein:

[0047]FIG. 1 illustrates, in simplified, cross-sectional schematic form,a MO medium according to a single-sided embodiment according to thepresent invention;

[0048]FIG. 2 illustrates, in simplified, cross-sectional schematic form,a MO medium according to a dual-sided embodiment according to thepresent invention.

[0049] It should be recognized that the various layers forming the layerstacks or laminates in the appended figures representing cross-sectionsof portions of MO media fabricated according to the inventivemethodology are not drawn to scale, but instead are drawn as to bestillustrate the features of the present invention.

BACKGROUND OF THE INVENTION

[0050] The present invention is based on the discovery that anultra-thin, “flash-layer” protective overcoat (“FLO”) and FLO protectiveovercoat/lubricant topcoat layer system comprised of specific materialscan provide optimal tribological performance of magnetically-induced,super-resolution (“MSR”) MO-based media, such as disks, with minimallubricant topcoat layer thicknesses and head-to-disk spacings (i.e.,flying heights) less than about 2 microinches (μ inch) for media withpolymeric substrates; less than about 1μ inch for media with metal,glass, or ceramic substrates with Ra of from about 3 to about 5Angstroms; and less than about 0.5μ inch for media with glass,glass-ceramic, or ceramic substrates with Ra of from about 2 to about 3Å. More specifically, according to the present invention, an ultra-thinFLO layer comprising an amorphous, hard, carbon-based,abrasion-resistant protective material, e.g., a carbon-baseddiamond-like material such as a-CN_(x) (where x=0.05-0.30), a-CH_(x)(where x=0.20-0.30), and a-CN_(x)H_(y) (where x=0.03-0.10 andy=0.15-0.30), is formed to cover the uppermost transparent dielectriclayer, typically a SiN_(x) material, formed over the MO read-out layerof such type MO media. The amorphous, diamond-like protective overcoatlayer has a thickness not greater than about 10 Å, e.g., about 5 toabout 10 Å, and can be formed by any of the physical vapor deposition(PVD) or chemical vapor deposition (CVD) methods conventionally employedfor depositing such type layers. By way of illustration, but notlimitation, a-CH_(x) layers may be deposited on suitable dielectricallycoated MO media substrates by AC sputtering of a 3 inch by 15 inchgraphite target at frequencies in the range of 40-400 KHz at a power inthe range of 0.5-2 KW in an atmosphere of 15% H₂/85% Ar. Similarconditions may be employed for forming a-CN_(x) and a-CN_(x)H_(y)coatings by use of N₂ and H₂—N₂ mixtures, respectively. Given thepresent disclosure and the objectives of the invention, determinationand selection of the parameters necessary for obtaining equivalentlyperforming diamond-like amorphous carbon-containing coatings by otherconventional film-forming techniques is considered within the ambit ofthe artisan for use in a particular situation.

[0051] The lubricant topcoat layer formed over the protective overcoatlayer, in embodiments according to the present invention, comprisesfluoropolyether or perfluoropolyether polymers such as, for example,perfluoropolyethylene (PFPE), and like materials available under thetradenames Fomblin ZDol, Fomblin AM2001, and Fomblin Z-Dol TX fromAusimont, Thorofare, N.J., and has a thickness not greater than about 25Å, e.g., from about 10 to about 25 Å.

[0052] The lubricant topcoat layer can be applied in any conventionalmanner, as by dipping in a dilute solution of the lubricant in asuitable solvent, e.g., a hydrofluorocarbon, or by spraying, etc.Desirably, the surface of the disk is preliminarily treated to be freeof impurities so that good bonding can occur between the functional endgroups of the lubricant polymer molecules and the substrate surface(i.e., the protective overcoat layer). The bonding of the lubricant tothe surface of the disk can be enhanced by cleaning the surface of theprotective overcoat layer with a mild plasma or a solvent rinse prior toapplying the lubricant.

[0053] By way of illustration, but not limitation, magnetically-induced,super-resolution (MSR) MO media provided with a 5-10 Å thick amorphous,carbon-based, diamond-like protective overcoat layer selected froma-CH_(x), a-CN_(x), and a-CN_(x)H_(y) and coated with 15-25 Å thicklubricant topcoat layers of Fomblin Zdol and Fomblin AM2001, providedexcellent tribological and stiction properties at reduced fly heights offrom about 2 to about 5μ inches for media with polymeric substrates andfrom about 0.5 to about 2μ inches for media with metal, glass, orceramic substrates.

[0054] An embodiment of the present invention comprises a single-sided,mnagnetically-induced, super-resolution (MSR) MO medium 10 employing theinventive flash layer protective overcoat (FLO) and FLO/lubricanttopcoat layer system and is illustrated in FIG. 1, wherein referencenumeral 1 denotes a substrate comprising a pair of major opposedsurfaces 1A and 1B. The material of the substrate is not critical forthe practice of the invention, and may be selected from polymers,metals, glass, and ceramics. The thickness of substrate 1 is also notcritical, but must provide adequate rigidity during rotation and staticperiods.

[0055] Formed on a first one (1A) of the opposing major surfaces ofsubstrate 1 is a layer stack, comprising, in overlying sequence fromsubstrate surface 1A: (a) a reflective, heat-sinking layer 2 about300-700 Å thick, preferably about 500 Å thick, typically comprising Alor an alloy thereof, e.g., AlCr, AlTi, etc.; (b) a first dielectricmaterial layer 3 about 100-400 Å thick, preferably about 100-200 Åthick, and substantially transparent to the wavelength(s) of the atleast one laser beam employed for writing and reading out information,typically selected from SiN_(x) (where x=ca 0.8-1.33), AlN_(x) (wherex=ca. 1-1.5), SiO_(x) (where x=ca. 1-2.0), and AlO_(x) (where x=ca.1-1.5); (c) a MO auxiliary, writing assist layer 4 comprising a RE-TMmaterial about 50-100 Å thick, typically selected from TbFe, TbFeCo, andFeCoX, where X is Dy, Gd, or Sm; (d) a MO writing layer 5 comprising aRE-TM material about 200-300 Å thick and having perpendicularanisotropy, large perpendicular coercivity, and high Curie temperature,typically selected from TbFe, TbFeCo, TbDyFeCo, TbFeCoX, and TbDyFeCoX,where X is Al, Y, or Nd, and DyFeCoX, where X is Y, Nd, or Al; (e) an MOexchange coupling layer 6 comprising a RE-TM material about 10-50 Åthick, for replicating the magnetic orientation of the MO writing layer5 and thereby increasing the coupling force between the MO writing layer5 and the MO read-out layer 8, typically selected from Gd, GdFe, GdFeSiand GdFeAl; or (f) a second dielectric material layer 7, for performingmagneto-static coupling between MO writing layer 5 and MO read-out layer8, the second dielectric layer 7 being about 5-50 Å thick andsubstantially transparent to the wavelength(s) of the at least one laserbeam employed for writing and reading out information, typicallyselected from SiN_(x), AlN_(x), SiO_(x), and AlO_(x), where x in eachinstance is as given above for layer 3; (g) a MO readout layer 8comprising a RE-TM material about 200-400 Å thick, typically selectedfrom GdFeCo and GdFeCoX, where X is Al, Nd, or Y, and GdFeCoXX′, where Xis Al, Nd, or Y, and X′ is Cr, Ta, or Nb, (h) a third dielectricmaterial layer 9, substantially transparent to the wavelength(s) of theat least one laser beam employed for writing and reading outinformation, i.e., about 400-500 Å for blue lasers and about 800-1200 Åfor red lasers, typically selected from SiN_(x), AlN_(x), SiO_(x), andAlO_(x), where x in each instance is as given above for layer 3; (i) anamorphous, diamond-like protective overcoat layer 11 not greater thanabout 10 Å Å thick, typically about 5 to about 10 Å thick and comprisinga material as described supra, i.e., a-CN_(x) (where x=0.05-0.30),a-CH_(x) (where x=0.20-0.30), or a-CN_(x)H_(y) (where x=0.03-0.10 andy=0.15-0.30); and (j) a lubricant topcoat layer 12 having a thickness ofabout 15-25 Å and comprised of a fluoropolyether or perfluoropolyetherpolymer compound, e.g., perfluoropolyethylene (PFPE).

[0056] It should be noted that MSR-MO media, such as described above,can have two alternate layer configurations, i.e., a magnetic exchangecoupling (configuration utilizing MO exchange coupling layer 6 and notrequiring second dielectric layer 7; and a magneto-static couplingconfiguration utilizing second dielectric layer 7 and not requiring MOexchange coupling layer 6.

[0057]FIG. 2 illustrates another, dual-sided embodiment corresponding tothe single-sided, first embodiment shown in FIG. 1 and described above.Such dual-sided media advantageously may be operated to record and readout information from both sides of a common substrate, and thus areuseful for increasing storage density. As for the dual-sided embodimentof FIG. 2, medium 20 comprises a second layer stack formed on the secondmajor surface 1B of substrate 1, in opposing relation to the first layerstack formed on the first major surface 1A, with both layer stacks beingidentically constituted as shown in FIG. 1.

[0058] Conventional techniques, such as PVD and/or CVD may be employedfor depositing each of the reflective, dielectric, auxiliary, writing,exchange coupling, and read-out MO RE-TM layers, as well as theprotective overcoat layers of the layer stacks of the above-describedembodiments, with sputtering generally being preferred. The lubricanttopcoat layer is readily deposited by conventional dipping techniques,as indicated above. Therefore, details of the deposition techniquesutilized for forming each of the layers of the layer stack are generallyomitted from the present disclosure for brevity and in order not tounnecessarily obscure the present invention.

[0059] Thus, the present invention advantageously provides, as by theuse of conventional processing techniques, high quality,magnetically-induced, super-resolution, MO information storage mediahaving novel, ultra-thin, abrasion-resistant, carbon-based, flash layerovercoats (FLO) imparting improved tribological properties thereto andtherefore suitable for use in high density storage devices requiringminimal head fly height.

[0060] In the previous description, numerous specific details are setforth, such as specific materials, structures, reactants, processes,etc., in order to provide a better understanding of the presentinvention However, the present invention can be practiced withoutresorting to the details specifically set forth. In other instances,well-known processing materials and techniques have not been describedin detail in order not to unnecessarily obscure the present invention.

[0061] Only the preferred embodiments of the present invention and but afew examples of its versatility are shown and described in the presentdisclosure. It is to be understood that the present invention is capableof use in various other combinations and environments and is susceptibleof changes and/or modifications within the scope of the inventiveconcept as expressed herein.

What is claimed is:
 1. A magnetically-induced, super-resolution (MSR),magneto-optical (MO) storage medium including at least one laminate oflayers comprising, in sequence from a substrate surface: an MO writinglayer; an MO exchange coupling layer or a magneto-static coupling layerfor increasing the recording density; an MO read-out layer; a dielectriclayer which is substantially transparent to the wavelength(s) of atleast one laser beam used for writing and reading out information storedin said medium; and an amorphous, abrasion resistant, carbon-basedprotective overcoat layer over said transparent dielectric layer.
 2. Themedium according to claim 1, wherein: said abrasion resistant protectiveovercoat layer comprises a material selected from the group consistingof: a-CN_(x), a-CH_(x), and a-CN_(x)H_(y).
 3. The medium according toclaim 2, wherein said protective overcoat layer has a thickness notgreater than about 10 Å.
 4. The medium according to claim 2, whereinsaid protective overcoat layer has a thickness of from about 5 to about10 Å.
 5. The medium according to claim 1, wherein said laminate furthercomprises a lubricant topcoat layer on said protective overcoat layer.6. The medium according to claim 5, wherein said lubricant topcoat layercomprises a fluoro polyether or perfluoro polyether lubricant.
 7. Themedium according to claim 6, wherein said lubricant topcoat layer has athickness of from about 15 to about 25 Å.
 8. The medium according toclaim 1, wherein said substrate includes a pair of opposed majorsurfaces and comprises a material selected from the group consisting ofpolymers, metals, glass, and ceramics.
 9. The medium according to claim8, wherein said laminate of layers comprises a stack of layers formed onone of said pair of opposed major surfaces, said layer stack comprising,in overlying sequence from said substrate: (a) a reflective, heatsinking layer formed on one of said pair of opposed major surfaces ofsaid substrate; (b) a first dielectric layer comprising a material whichis substantially transparent to said at least one laser beam wavelength;(c) an MO auxiliary, writing assist layer comprising a rareearth/transition metal (RE-TM) material; (d) an MO writing layercomprising an RE-TM thermo-magnetic material having perpendicularanisotropy, large perpendicular coercivity, and high Curie temperature;(e) an MO exchange coupling layer comprising an RE-TM material, forreplicating the magnetic orientation of the MO writing layer and therebyincreasing the coupling force between the MO writing layer and the MOread-out layer; or (f) a magneto-static coupling layer comprising asecond dielectric layer comprising a material which is substantiallytransparent to said at least one laser beam wavelength and performsexchange decoupling; (g) an MO read-out layer comprising an RE-TMmaterial having a small coercivity; and (h) a third dielectric layercomprising a material which is substantially transparent to said atleast one laser beam wavelength; wherein said protective overcoat layeris formed on said third dielectric layer.
 10. The medium according toclaim 9, further comprising a lubricant topcoat layer over saidprotective overcoat layer.
 11. The medium according to claim 9, wherein:said reflective, heat sinking layer (a) comprises aluminum or an alloythereof; each of said first, second, and third substantially transparentdielectric layers (b), (f), and (h) comprises a material selected fromthe group consisting of: SiN_(x), AlN_(x), SiO_(x), and AlO_(x); said MOauxiliary, writing assist layer (c) comprises an RE-TM material selectedfrom the group consisting of: TbFe, TbFeCo, and FeCoX, where X is Dy,Gd, or Sm; said MO writing layer (d) comprises an RE-TM materialselected from the group consisting of TbFe, TbFeCo, TbDyFeCo, TbFeCoX,and TbDyFeCoX, where X is Al, Y, or Nd, and DyFeCoX, where X is Y, Nd,or Al; said MO exchange coupling layer (e) comprises an RE-TM materialselected from the group consisting of Gd, GdFe, GdFeSi, and GdFeAl; andsaid MO read-out layer (g) comprises an RE-TM material selected from thegroup consisting of: GdFeCo and GdFeCoX, where X is Al, Nd, or Y, andGdFeCoXX′, where X is Al, Nd, or Y and X′ is Cr, Ta, or Nb.
 12. Themedium according to claim 11, comprising another layer stack, identicalto the abovesaid layer stack, formed on the other one of said pair ofopposed major surfaces of said substrate.
 13. A magnetically-induced,super-resolution, magneto-optical (MO) storage medium including at leastone laminate of layers comprising, in sequence from a substrate surface:an MO writing assist layer; an MO writing layer; an MO exchange couplinglayer or a magneto-static coupling layer in contact with the MO writinglayer for increasing the recording density thereof; an MO read-outlayer; a dielectric layer which is substantially transparent to thewavelength(s) of at least one laser beam used for writing andreading-out information stored in said medium; an amorphous, abrasionresistant, carbon-based, protective overcoat layer over said transparentdielectric layer, said protective overcoat layer having a thickness notgreater than about 10 Å and comprising a diamond-like material selectedfrom the group consisting of: a-CN_(x), a-CH_(x), and a-CN_(x)H_(y); anda lubricant topcoat layer having a thickness of from about 15 Å to about25 Å on said protective overcoat layer, said lubricant topcoat layercomprising a fluoro polyether polymer or a perfluoro polyether polymer.14. The medium according to claim 13, wherein said substrate includes apair of opposed major surfaces and comprises a material selected fromthe group consisting of: polymers, metals, glass, and ceramics.
 15. Themedium according to claim 14, wherein said laminate of layers comprisesa stack of layers formed on one of said pair of opposed major surfaces,said layer stack comprising, in overlying sequence from said substrate:(a) a reflective, heat sinking layer formed on said one of said pair ofopposed major surfaces of said substrate and comprising aluminum or analloy thereof; (b) a first dielectric layer comprising a material whichis substantially transparent to said at least at least one laser beamwavelength and selected from the group consisting of: SiN_(x), AlN_(x),SiO_(x), and AlO_(x); (c) an MO auxiliary, writing assist layercomprising an RE-TM material selected from the group consisting of TbFe,TbFeCo, and FeCoX, where X is Dy, Gd, or Sm; (d) an MO writing layercomprising an RE-TM thermo-magnetic material having perpendicularanisotropy, large perpendicular coercivity, high Curie temperature, andselected from the group consisting of: TbFe, TbFeCo, TbFeCoX, TbDyFeCo,and TbDyFeCoX, where X is Al, Nd, or Y, and DyFeCoX, where X is Al, Nd,or Y; (e) an MO exchange coupling layer comprising an RE-TM materialcomprising Gd, GdFe, GdFeSi, or GdFeAl, for replicating the magneticorientation of the MO writing layer and thereby increasing the couplingforce between the MO writing layer and the MO read-out layer; or (f) amagneto-static coupling layer comprising a second dielectric layercomprising a material which is substantially transparent to said atleast one laser beam wavelength, selected from the group consisting of:SiN_(x), AlN_(x), SiO_(x), and AlO_(x); (g) an MO read-out layercomprising an RE-TM material selected from the group consisting of:GdFeCo and GdFeCoX, where X is Al, Nd, or Y, and GdFeCoXX′, where X isAl, Nd, or Y and X′ is Cr, Ta, or Nb; and (h) a third dielectric layercomprising a material which is substantially transparent to said atleast one laser beam wavelength and selected from the group consistingof: SiN_(x), AlN_(x), SiO_(x), and AlO_(x); wherein said protectiveovercoat layer is formed on said third transparent dielectric layer andsaid lubricant topcoat layer is formed on said protective overcoat layer16. The medium according to claim 15, comprising another layer stack,identical to the abovesaid layer stack, formed on the other one of saidpair of opposed major surfaces of said substrate.
 17. Amagnetically-induced super-resolution, magneto-optical (MO) storagemedium comprising: a substrate; and means for protecting the surface ofsaid medium.